This paper describes techniques allowing the determination of three-dimensional orientations of fillers, in fiberglass reinforced thermoplastics, using scanning electron microscopy. To measure orientation angles (in-plane and inclination angles), it's necessary to individualize each particle. Segmentation operations are done by watershed on a filtered distance function. Two sectioned surfaces with different section angles must be studied, to construct the total 3D orientation distributions. A good representation of results is given by density stereographic projection, that offers very synthetic informations.